Electric products operate while consuming electric energy. Since electric products consume electric energy, the amount of electricity consumption or electricity charge may be a sensitive matter to users.
As energy consumption increases, it is necessary to develop more energy sources and produce more electric energy. However, electricity generation causes a large amount of greenhouse gas and environmental problems such as global warming. To reduce emission of greenhouse gas, particularly, carbon dioxide, alternative energy sources have been developed such as wind power, solar light, solar heat, geothermal power, tidal power, and water power as well as nuclear power and fuel cells.
Along with this, a smart grid has been proposed as the next generation power grid to improve energy efficiency by realizing two-way and real-time information exchange between power providers and consumers in a way of applying information technology (IT) to the existing power grid.